Variable inductance system



Jan. 17, 1933. c. F. RUDOLPH VARIABLE INDUGTANCE SYSTEM Filed July 20, 1931 3 Sheets-Sheet l l a S F INVENTOR. Com/ w 55 M01 0 I ATTORNEY 3 a m w 6 Jan. 17, 1933. c. F. RUDOLPH VARIABLE INDUCTANCE SYSTEM 3 Sheets-Sheet 2 Filed July 20. 19.'51

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VARIABLE INDUCTANCE SYSTEM Filed July 20, 1951 3 Sheets-Sheet 3 Emmi % INVENTOR. Ks

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ATTORNEY I Patented Jan. 17, 1933 UNITED STATES PATENT OFFICE CORRIE F. RUDOLPH, OF WASHINGTON, DISTRICT OF COLUMBIA VARIABLE INDUCTANCE SYSTEM Application filed July 20,

19 tions that are simultaneously variable in a predetermined order.

Another object of my invention is to provide a construction of continuously variable p inductance coils having parts variable in equal increments in opposite directions from a common center.

Still another object of my invention is to provide a construction of high frequency inductance system adapted for operation with 9 push pull amplifier circuits in which parts of the inductance system in the different push-pull amplifier circuits are continuously variable in equal increments in opposite d1- rections from a common center under control of the same adjusting means.

A further object of my invention is to provide a construction of variable inductance coil having separate portions of a. helical inductance symmetrically arranged with respect to a cent 'al adjusting shaft with means operated by the adjusting shaft for driving a pair of contactors in opposite directions from a common center for selectively vary- 7 ing' the separate portions of said inductance 0 in equal increments.

Other and further objects of my invention reside in the construction of variable inductance system in which a drive shaft extends axially through the inductance system and operates to drive movable contactors inopposite directions from a common center along said inductance system, as will be more fully understood from the specification hereinafter following by reference to the accompanying drawings, in which:

Figure 1 is a side elevation of the inductance system ofmy invention; Fig. 2 is an end view of the drive mechanism for effecting an adjustment of the effective inductance in the inductance system; Fig. 3 is a lateral cross- 1531. Serial No. 552,051.

sectional view taken through the inductance system on line 33 of Fig. 1; Fig. 4 is a longitudinal cross-sectional view taken through the inductance system and operating mechanism therefor; Fig. 5 is a fragmentary cross-sectional view taken through the actuating mechanism of the inductance system on line 55 of Fig. 1; Fig. 6 is a fragmentary side elevational view of the parts of the inductance system connected in series; and F ig. 7 is a schematic view showing the circuit arrangement for the adjusting con tactors on the inductance system of my invention as used in a push-pull amplifier circuit.

A continuously variable inductance coil with a fixed condenser connected in circuit therewith will cover a larger band of frequencies than a fixed coil with a variable condenser, due to the large ratio between 7 maximum and minimum inductance values which it is possible to obtain with such an inductance coil. If the variable capacity method of tuning over a range of frequencies is used, the ratio between the maximum and minimum values is rather low particularly at the higher frequencies where the distributed capacity is a large portion of the total capacitv.

The use of a push-pull circuit is highly desirable in a radio transmitter operating in the hi her frequency bands, in fact it is possible to operate at a higher frequency with the push-pull system than can be done with the single ended circuit. The employment of a push-pull circuit requires that the inductance and capacity elements be arranged symmetrically. If a continuously va riable inductance coil is used in the input or output circuit, it must also be arranged symmetrically. The apparatus of my invention provides an inductance in which the two halves of the coil are duplicates of each other and the contacts of the coil are arranged to maintain equal amounts of inductance in the two halves of the circuit with a given movement of the control member.

Referring to the drawings, the two halves of the inductance coil 8 and 8a are supported between insulating end members 26 and 30 ilk by means of insulating strips 1, 2, 3, 4, 5 and 6, said strips having slots for the rigid support and spacing of the turns of the coils. The ends of the two halves of the coils 8 and 8a are bent at 812 and 80 to connect to metal end pieces and 36 which form the end terminals of the coil. The adjacent ends of said coils 8 and 8a are joined at 8d to form a continuous coil and in order to form a connection for a path including a condenser 8a to ground.

The brushes 13 and 13a are adapted to rotate in opposite directions and thereby cut in or out required inductance by short circuiting the turns remaining between the brushes and the terminals 8?) and 8c. Brushes 13 and 13a are carried by means of sleeves 7 and 7a which are slidably mounted upon and slotted to make good electrical contact with tube members 57 and 58. Brush 13 is caused to rotate and track with coil 8 by the simultaneous opposite rotation of tube member 57 and threaded member 51 and due to said opposite rotation the pitch of threaded member 51 must be equal to one-half the pitch of the coil 8. The opposite rotation of members 57 and 51 is accomplished by means of a bevel reversing gear 9 and 9a and idler gears 10 and 10a, said gear 9 being connected 'to screw threaded member 51 and gear 9a connected to member 57. Screw member 51 is also connected to the control crank 11 which is operated from the front of panel through insulated universal joint 71 and freduction gears 12 and 12a. lhe control crank 11 has connected thereto a conventional counter 15 by means of a set of bevel gears 16 for indicating the amount of inductance included in the amplifier circuit. Brush 13a is caused to rotate and track with coil 8a by means of a rotating tube member 58 and an inwardly extending stud member 19a having a thread pitch equal to the pitch of coil 8a which engages the threads on the fixed screw threaded member 52. Tube member 58 is rotated by means of member 51 to which it is rigidly connected through an insulating block 29, as shown. The connecting means consists of a bracket 61 screwed onto block plug 62 is swaged and keyed against independent movement by pin member 63. The

tube 58 is secured to plug 62 by means of pin 62a for imparting rotative movement to tube 58 in accordance with the rotation of the screw threaded shaft 51. The block 29 is connected with shaft 51 by means of bracket member64t into which the end of shaft 51 is directly swaged, the bracket member 64 being secured to block 29 by means of screws 6 164. A pin 65 serves to interlock bracket 6 more rigidly with shaft 51 as shown. The stationary shaft 52 which is supported by screws 66 from terminal member 36 terminates at 52a in spaced relation to the end of plug 62 thereby leaving tube 58 free to revolve around stationary shaft 52. Sleeve members 7 and 7a are adapted to slide on their respective tube members 57 and 58 under control of stud members 19 and 19a, which project through the slots 57a and 58a in the tubes 57 and 58 and engage the threaded groove of members 51 and 52, while sleeves 7 and 7a move longitudinally over the tube members 57 and 58. To prevent undue friction on the stud mem ers 16 and 19, I provide shoe members 74 which are adapted to pivot on the studs while guiding the sleeve members 7 and 7a. Good electrical contact is maintained between members 57 and 8b and members 58 and 80 by means of brush members 16 and 37. Member 36 is maintained in spaced relation to end piece 30 by means of spacers 38. Member 15 is maintained in spaced relation to end piece 26 by means of spacers 59. Mounting plate 14 for rotation counter 15 is supported on insulating posts 18 and 18a. Good electrical contact through hinged joint on brushes 13 and 13a is maintained by flexible copper strips 14 and; 14a.

The construction of the inductance system is such that both portions of the inductance may be readily mounted within the frame str cture, and adjusted from the common control 11. It will be observed that contactors 13 and 13a are movable in opposite directions from a common center for effectively'including equal increments of an inductance in the circuits with which the portions of inductance are associated.

In Fig. 7 I have shown a form of pushpull am liiier circuit including electron tubes 72 and 3. The grid electrodes 72a and 73a are connected to the movable contactors 13 and 13a, respectively. By shifting contacts 13 and 13a in opposite directions from the center 8d the effective inductance in each portion of the inductance is changed by short circuiting the turns between the movable taps and the ends of the inductance. .The movement of the contactors is in equal increments in opposite directions from a common center and is brought about by the me chanical construction of the control. means.

It will be observed that both screw threaded shaft 51 and the concentrically disposed tubular member 57 are rotatable in opposite directions. The shaft 52 on the other hand is stationary while tubular member 58 is rotatable at the same rate of movement as screw threaded shaft 51. The difference in pitch etween screw threaded shaft 52 and screw threaded shaft 51 is in a ratio of two to one by reason of the opposed rotation of shaft and tube 57 and the rotation of tube 58 with respect to stationary shaft 52.

The assembly. of the frame comprising strips 1, 2, 3, l, 5 and 6 greatly simplified by the construction shown herein. The parts of the frame are constructed of synthetic porcelain or ceramic or victron material so that special means such as I have shown must be employed in the assembly. The strips 1-6 are pierced laterally at their ends to receive pin members 75. The opposite projecting ends of the pin members 7 5 are laterally screw threaded to receive the ends of securing screws 76 which pass through panel members 26 and 30 having heads 76a. The screws 7 6 hug opposite sides of the strips and thereby serve to center the strips in. position with respect to the end panels 26 and 80 as shown. This construction avoids any necessity of screwing directly into the material of the strips.

A high degree of precision in the adjustment of inductances in the different branches of the associated circuits is obtained with the structure of my invention and while I have described my invention in one of its preferred embodiments, I desire that it be understood that modifications may be made and hat no limitations are intended other than are imposed by the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States is as follows:

1. In a variable inductance system, a frame, a helical inductance having the turns thereof supported by said frame, a shaft extending axially through said frame, said shaft having two portions each having screw threads cut thereon, the screw threads on one portion being pitched differently from the screw threads on the other portion, contactors engaging turns of said helical inductance and means interposed between said contactors and the portions of said shaft for driving said contactors through equal. angular distances in opposite directions with respect to a common center.

2. An inductance system comprising a frame structure, a helical inductance mounted within said frame structure, a rotatable shaft member extending axially through said inductance, said rotatable shaft member being divided into separate portions, each iortion being independently screw threaded, a contactor driven by each of the portions of said shaft and means for rotatably driving one portion of said shaft for imparting movement to each of said contactors through equal angular increments in opposite directions with respect to a common center.

3. An inductance system comprising a frame structure, an inductance carried by said frame structure, a rotatable system extending through said frame structure, said rotatable system including a rotatable screw threaded shaft member, a tubular member coupled thereto and an insulated coupling therebetween, a stationary screw threaded shaft member carried by said frame structure and projecting through the tubular member to a position terminating short of said insulated coupling, a pair of contactors engaging the turns of said inductance, and means intercon-- necting said contactors with said screw threaded shaft members for imparting movement to said contactors through equal angular increments in opposite directions from a common center under control of said rotatable shaft member.

4:. An inductance system comprising a frame structure, a helical inductance carried by said frame structure, a rotatable system extending through said frame structure, said rotatable system including independent tubular members and independent screw threaded shaft members, one of said screw threaded shaft members being directly coupled with the coextensive tubular member, means for driving the tubular member which encloses said last mentioned screw threaded shaft member in a direction opposite to the direction of movement of the last mentioned screw threaded shaft member, the other screw threaded shaft member being rigidly connected with said frame structure within the coextensive tubular member, contactors engaging the turns of said inductance and means carrying said contactors and engaging said screw threaded shaft members for effecting movement of said contactors along said inductance in equal angular increments in opposite directions with respect to a common center.

5. An inductance system comprising a frame structure, an inductance carried by said frame structure, a rotatable system eX- tending through said frame structure, said rotatable system including a divided rotataable member comprising a screw threaded shaft portion and a coextensive tubular portion, a rotatable tubular portion concentrically positioned with respect to said screw threaded shaft portion and adapted to be driven in a direction opposite to the direction of movement of said screw threaded shaft portion, a screw threaded member extending axially into said coextensive tubular portion and separate contactors slidably mounted over said tubular members and having means engaging said screw threaded shaft portion and said screw threaded member for effecting equal angular displacements of said contactors along the turns of said inductance in opposite directions with respect to a common center.

6. An inductance system comprising a frame structure, an inductance carried by said frame structure, a rotatable system extending through said inductance, said rotatable system including a positively driven screw threaded shaft and a coextensive tubular member insulatingly coupled thereto, a screw threaded member carried by said frame structure and projecting axially into said c0- extensive tubular member, a rotatable tubular member concentrically disposed over said positively driven screw threaded shaft member, each of said tubular members having longitudinally extending slots therein, sleeve members mounted for longitudinal movement over said tubular members and contactors engaging the turns of said inductance and supported by said sleeve members, said contactors being variable in equal increments along said inductance with respect to a common center.

7 An inductance system comprising a frame structure, a helical inductance supported by said frame structure, a rotatable system extending through said frame structure, said rotatable system comprising composite screw threaded shaft members and concentrically disposed tubular members, one of said screw threaded shaft members being insulatingly coupled with the coextensive tubular member, means for rigidly securing the other of said screw threaded shaft members with respect to said frame structure, means for positively, driving the other of said tubular members in a direction opposite to the direction of rotation of the first mentioned shaft member, sleeve members slidable over said tubular members and contactors extending from said sleeve members and engaging the turns of said inductance, said con tactors being movable through equal angular increments along said inductance in opposite directions with respect to a common center.

8. In an inductance system, a frame structure comprising a pair of end plates and a plurality of interconnecting strip members of insulated material, an inductance supported by said strip members with the turns thereof disposed in predetermined spacial relati-on, pins projecting laterally through each end of said strip members and screw devices extending through said end plates and engaging opposite ends of said pins on each side of said strips for maintaining said strips in rigid position with respect to said end plates.

CORRIE F. RUDOLPH. 

